The present invention relates to rotary drum equipment of the type that is used with helical scan recording/reproducing equipment and is especially suitable in a double azimuth head and to recording/reproducing equipment using such a head.
In recording/reproducing equipment of the helical scan type, a rotary upper drum is provided with an opening (hereinafter referred to as a "drum window") in the outer periphery thereof at a part opposing a lower stationary drum. A magnetic head is installed into the drum window so that it projects slightly from the upper drum surface. The rotating magnetic head slides on a magnetic tape that is transported over the surface of the drum equipment and records/reproduces a signal to/from the tape.
In view of the high speed sliding movement of the head on the surface of the tape, the magnetic head and the magnetic tape must keep in good contact with each other in order for the magnetic head to provide a good reproducing output. Rotary drum equipment that requires high picture quality and the recording of a large amount of information, such as for a digital VTR, requires a speed-up of the drum rotation, a mounting of multi heads on the drum and short wave-length recording. In such a drum, it is easy for deterioration of the contact between a magnetic head and the magnetic tape to occur, as well as enlargement of the spacing between a head and the tape, thereby causing deterioration of the reproducing output. Especially, in the recording of a short wavelength of less than 1 .mu.m, the deterioration of the reproducing output is extreme.
In a magnetic head that consists of a single head chip with a single gap azimuth (hereinafter referred to as a "single azimuth head"), a groove is provided on the surface of an upper drum, as shown in Japanese patent Laid-open Publication 61-214271. The air adjacent the drum during the rotation of the upper drum runs away through this groove, and so the flying height of the magnetic tape can be reduced. As a result, good contact is achieved between a magnetic head and the magnetic tape.
In a magnetic head that consists of two head chips that have two different gap azimuths (hereinafter referred to as a "double azimuth head"), the spacing of the magnetic heads in the drum window was set according to the following condition, as described in Japanese patent Laid-open Publication 3-93020. The space between the preceding head and the drum window was made smaller than the space between a succeeding head and the drum window in the direction of rotation. This causes the contact and the wear to become even at the preceding head and the succeeding head.
As is disclosed in the above-referenced publication concerning the single azimuth head, a groove carved in an upper drum acts to set the air between a magnetic tape and an upper drum free and to provide good contact between the tape and the head.